Electric quantity standard



July 12, 1949. T. A. RICH ELECTRIC QUANTITY STANDARD ,Filed March 21, 1946 Inventor: Theodor-e A. Rich, by MW His Attorney Patented July 12, 1949 ELECTRIC QUANTITY STANDARD Theodore A. Rich, Schenectady, N. Y., allignor to General Electric Company, a corporation oi New York Application March 21, 1948, Serial No. 655,982

11 Claims. (01. ass-cs) My invention relates. to an electric quantity standard and more particularly to an electric network for prcvidinga secondary standard of an electric quantity having the characteristics of a standard cell.

It is an object of my invention to provide a new and improved standard of an electric quantity.

It is another object of my invention to provide a new and improved electric network for providing a secondary standard of voltage from which different components of voltage may be obtained having the same characteristics as the voltage of a primary standard such as a standard cell.

It is a further object of my invention to provide a new and improved electric network suitable for use as a current standard.

In accordance with the illustrated embodiment of my invention, I provide an electronic network which utilizes a constant source of volta e such as a standard cell as'the primary reference voltage in combination with a compensated galvanometer and an associated electronic control circuit to provide a secondary voltage standard having the characteristics of the constant source of voltage. The secondary voltage standard is, in turn, associated with a second compensated galvanometer and its associated electronic circuit to compare the secondary standard with an electric quantity, such as the voltage or current, of a circuit or device subject to variations in its electrical condition.

2 nectedto be energized by an .exciter 4 having a separately energized field winding 5. The exciter field winding I is connected to be energized from a. controlled rectifier 8 which comprises atransformer 1 having a primary winding 8 and a secondary winding 8 connected through a pair of electronic tubes l and II which are arranged for bi-phase half-wave rectification. The primary winding 8 of the rectifier transformer I is connected to be energized from an altemating current supply bus l2 which, in turn, is connected to be energized from a main alternating current supply circuit l3, preferably through a constant voltage transformer It, to insure a substantially constant voltage for energizing the various component circuits of the regulator.

Electronic tubes l0 and II are preferably of the My invention will be better understood from the following description taken in connection with the accompanying drawing, and itsscope will be pointed out in the appended claims.

The single figure of the accompanying drawing is a diagrammatic illustration of one embodiment of my invention as utilized in controlling a direct current generator.

Referring to the drawing, I have shown an embodiment of my invention utilized as a current standard in connection with the control of a direct current dynamo-electric machine which is shown in a simplified form for the purpose of illustrating how my current standard may be applied. The details of such a dynamo-electric machine control system are described and claimed in Patent No. 2,452,611, granted November 2,

gaseous type, such as of the thyratron type as illustrated, and each tube'is provided with a control electrode to control the desired current for energization' of the exciter field winding 5. Tube III is provided with an anode iii, a cathode l8 and a control grid l1, while tube ii is similarly provided with an anode i8, a cathode is and a control grid 20. One' terminal of field winding 3 is connected to a midpoint 9' of the secondary winding 9 and the other terminal of field winding 5 is connected to a junction point 2i of the oathodes i8 and I9 in a conventional manner'for bi-phase rectification. The heater circuits for cathodes i6 and I! have been omitted to avoid complicating the drawing, but such heater cir cuits would be provided for these tubes as well as for the other tubes later described in any conventional manner well known in the art. The control grids I! and are-connected to be controlled through a suitable phase shifting means or network 22 which, as illustrated, comprises a transformer 23 having a primary winding 24, connected to be energized from the alternating current supply bus 12, and a secondary winding 25 provided with an electrical midpoint terminal 25". A resistor 28 and a saturable reactor 21 provided with a direct-current saturating winding 28 are connected in series relation across the end terminals of the secondary winding 25. Av

junction terminal 29 is provided between the resistor 26 and the saturable reactor 21. A grid transformer 30 is provided to supply a voltage from the phase shift circuit 22 which is variable in phase with respect to the voltage impressed upon the anode-cathode circuits-of tubes Ill and H. Grid transformer 30 comprises a primary winding 3| connected between the electrical midll point 25' and the Junction terminal 29, and a secondary winding 82 having a midpoint terminal 83 connected to the cathode junction terminal 2| with the end terminals thereof connected through grid resistors 84 and 85 to grids l1 and 28, respectively.

The regulator which controls the energization of generator I by controlling the rectifier 8 comprises a voltage standard section 88 and a voltage amplifier section 81. These two sections along with the rectifier 8 and its phase shift circuit 22 may be conveniently mounted on the same panel for unit enclosure as indicated by the dotted rectangle 88. Power "supply for the voltage standard 88 may be obtained from a conventional power regulated supply unit which is connected to energize the conductors 88. The control of the rectifier 8 is effected by means of the phase shift circuit 22 by varying the saturation of reactor 21 by means of its direct current winding 28. The energization of winding 28 is obtained by connecting this winding across the voltage standard conductors 88 through a controlled electronic tube 48. The tube 48 is illustrated as being of the high vacuum type with an anode 4|, a cathode 42 and a control grid 43. A voltage divider comprising resistors 44 and 45 is connected to be energized in accordance with the voltage of conductors 88. A junction terminal 48 is provided between the resistors 44 and 45 and is connected to the cathode 42 of tube 48 to maintain the cathode of tube 48 at some predetermined voltage negative with respect to the positive bus of conductors 88. A by-pass capacitor 41 is connected across the saturating coil 28.

In accordance with my invention, 1 provide a current standard" which comprises an electronic control network'preferably encased in a constant temperature box or compartment indicated by the dotted rectangle 48. The current standard may be divided into four circuits which may be identified as a "reference fiuxmeter 49, a monitor fiuxmeter" 58, a "feed-back circuit 5| and a compartment heater circuit 52. The reference fluxmeter 48 comprises, broadly speaking, a compensated galvanometer of the type described and claimed in Patent No. 2,356,608, granted August 22, 1944 upon an application of Lorin OBryan. The term compensated as used in connection with this galvanometer means that the meter does not tend to drift either to a 4 produce an instrument of extreme sensitivity. Manual control of the fluxmeter position is obtained by means of a reversing switch 8| which connects the coil 54 for energization of either polarity from a battery 82 through a resistor 88. The switch 8| is biased to a neutral contact position by suitable spring means 8|. The primary standard in the current standard is a constant and substantially non-variable source of voltage such as a standard cell 84, the voltage of which is compared with the voltage drop across a resistor 88. The resistor 85 and a control tube 88 are connected across bus conductors 81 and 88 which are energized from the regulated voltage supply input conductors 88 through terminals 88 and 18. A manual control switch 88' 88 is provided with an anode 18, a cathode I1 zero or to a .stop position at either end of its travel. Since the specific details of the fluxmeter per se form no part of my invention, I have illustrated. the essential elements of the device in a simplified diagrammatic form as comprising a magnetic core 53 within which is suspended a coil winding 54 by means of wires 55 and 58, preferably of gold alloy. A mirror 51 is mounted on the wire 58. The fluxmeter is similar to a direct current milliammeter except that it has no restrainingtorque and very little friction in view of the gold wire suspension. Whatever res-training torque is introduced by the gold wire suspension is canceled out by a tiny permanent magnet 58 operating in the stray field of the magnet 53. Adjustment of the stray field is obtained by soft iron magnetic field shunting elements 59 and 88 which are adjustable towards or away from the magnet 58. The closer these two soft iron pieces are to the small torque-com pensating magnet 58, the less the restraining torque is canceled out, and vice versa. By proper proportioning of these parts it is possible to substantially cancel the restraining torque and thus and a control electrode 18. An anode resistor 19 is connected in series with anode l8 and the cathode I1 is connected to the adjustable tap 15'. A voltage divider comprising in series relation a resistor 88, a light sensitive device such as phototube 8|and a resistor 82 is connected between the adjustable tap I4 and to conductor 88. The grid "of tube 88 is connected to a junction terminal 88 between the phototube 8| and the resistor 82. The resistance of the phototube is controlled in accordance with the amount of light striking its target as directed thereon by mirror 51 of the fiuxmeter from a source of light 84, and thereby controls the conductivity of tube r 88 by controlling the potential of grid l8.-

placing the reversing switch 8| in one position or the other, a voltage is impressed on the fluxmeter coil 54 from battery 82 to force coil 54 to rotate in one direction or the other to a given position. The phototube 8| and resistors and 82 form a voltage divider circuit to control the grid 18 of the tube 88. As soon as tube 88 is rendered conductive by the initial positioning of coil 54, relay 1| picks up to close its contacts 12 and thereby connect coil 54 of the fluxmeter for energization in accordance with the difierential voltage of the standard cell 84 and the drop across resistor 85. Since the fluxmeter will rotate in one direction as long as voltage of one polarity is impressed across it and in the opposite direction if the voltage is reversed, the fluxmeter will hold the anode current of tube 88 at a value which will produce a voltage across resistor 85 exactly equal to the voltage 01' standard cell 84. If the anode current of tube 88 starts to drop, the higher voltage of the standard cell will cause the fiuxmeter to swing the light beam further on the phototube 8| to increase in a positive direction the potential of grid 18 and thereby increase the current through resistor 85 and establish a state of voltage equilibrium with the voltage of the standard cell. If for any reason, such as failure of the light source 84, the anode current to tube 88 drops below the predetermined value required'to givethe desired drop across resistor 85, the relay II will drop out and open the circuit of standard cell 64. After reestablishing the light source, the light beam will have be projected on the phototube 9| by means manual control switch BI which may be mo-- mentarily operated to an energizing position to position and that a standard voltage equal to the voltage or the standard cell 54 will be obtained across resistor 65. The standard voltage obtained across resistor 65 will be as standand as that of the standard cell, making it possible to tap off diflerent voltage components having the characteristics of the voltage of the standard cell without drawing any current from the standard cell. A standard cell cannot be used as a standard ii. any appreciable current drain exists. and will not recoverits standard voltage after this drain has been removed. With the arrangement described herein, the drain on the standard cell is so low that the properties of the standard cell are not adversely affected. This is possible because the compensated galvanometer is so sensitive that it will balance the voltages and the drain is in the thousandths of microamperes. This standard voltage drop across resistor 65 is divided into steps by the arrangement of resistors 85, 89, 81 and 98. Resistors 85 and 81, which may be fixed resistors, are connected in series relation with resistor 96 of the variable type across the voltage standard resistor 95. The resistor 86 is provided with two adjustable arms 96' and 86" which are adjusted in spaced relation onthe resistor 86 and connected respectively to the terminals of resistor 88. If desired, the arms 85' and 86" may be tied together mechanically to preserve a given spaced relation between the arms and for operation thereof in unison. The resistor 88 is alsoprovided with an adjustable arm 89.

The monitor fiuxmeter 50 may be substantially the same as the reference fluxmeter 49 except that it may be provided with a lower resistance coil 90 cooperating with its magnetic core 9!. The coil 90 is suspended by gold alloy wires 92 and 93 and a mirror 94 is mounted on the wire 93. The adjustment for the stray field is obtained by the small magnet 95 and the soft iron pieces 96 and 91 placed in the stray field oi the magnet 9|. Manual control of the fluxmeter 50 is obtained by means of a reversing switch 93 biased to aneutral contact position by suitable means indicated by the springs 98'. The switch 99 controls the monitor fluxmeter coil 90 through a resistor 99 from battery 62 in the same manner as switch GI controls the reference fluxmeter coil 54. A voltage divider comprising resistors I and IIII connected in series relatlon across conductors 61 and 68 of the regulated voltage supply is provided for the controlled circuit of the monitor fluxmeter 50. The resistors I00 and IM are provided respectively with adjustable arms I02 and I03 A voltage divider comprising a resistor I04, alight sensitive device such as a phototube I05 and a resistor I06 is connected in series relation between the adjustable arm I02 of resistor I00 and the bus conductor 68. The resistance of the phototube I05 is controlled in accordance with the amount ofiight striking its target asdirected thereon by the mirror from a light source I 01.

A control circuit for the monitor fluxmeter comprises a'resistor ittconnected in series rela- 5 tion with transformer I09 (constituting a mutual inductance) and a controlled electronic tube lit between the regulated bus conductor 61 and the adjustable arm I99 on resistor Hill. The tube ilt is provided with an anode ill, a cathode I if. and a control grid lit. The grid H3 is connected to a junction terminal lid between the phototube Hi5 and the resistor Hit, A capacitor H5 is connected between the grid lit and its cathode M2 for preventing the grid from changing its potential too quickly. The mutual inductance oi transformer we comprises a primary winding H9 connected in series with the anode-cathode circuit of tube lit and a secondary winding Ill. The secondary winding II! is the monitor fiuxmeter through a resistor II8 to the negative terminal of a current shunt I.I9 connected in the positive output conductor 2 of generator l. The positive terminal of shunt H9 is connected to the positive bus conductor 61 and hence also to the control circuit including primary winding IIB of the mutual inductance and the controlled tube H0. The monitor fiuxmeter thus compares the component of voltage across shunt II9 with the voltage component derived from the secondary standard constituted by the voltage divider resistor 88 and the associated resistors 85, 96 and 81. This comparison circuit may be traced from the positive terminal of shunt H9, conductor 51, resistors 95,

36 and 88 and adjustable arm 39, through coil 90, thence through secondary winding II? to the negative terminal of shunt H9. The mutual inductance I09 having its primary winding H6 in series relation with tube IIfi slows down any change in energization of the coil 99 by inducing a voltage therein which tends to rotate the element 90 in such a direction as to oppose the change of current in the circuit of tube IIO. A double-poled switch I20 having one set of contacts IZI and another set of contacts I22 is provided to connect a voltage regulating low tube I23 through contact I22 to the anode of tube H0 and to the regulated bus conductor 68, and also to connect the glow tube I23 through contact I2I to the grid circuit of tube 40 by means of the deed-back circuit 5| now to be described.

The feed-back circuit 5| is utilized to insert a voltage component in the monitor fiuxmeter in accordance with voltage changes of generator I andcomprises a voltage divider I24 connected to, be responsive to the voltage of generator I and includes in series relation adjustable resistors I25, I26, I21 and I28 connected across the positive and negative terminals of generator i through a fixed resistor I29. The resistor I23 is provided with an adjustable arm I30 which is connected through series connected resistors I3I and I32 to the contacts I2I of switch I20. A junction terminal I33 is provided between the resistors I3I and I32 and is connected to the grid 43 of tube 40 through a grid resistor I34. A capacitor I35 is connected across the voltage divider I24 and with resistor I29 forms a filter circuit to reduce the voltage ripple on the voltage divider I24. A capacitor I35 is charged through a resistor I31 from the negative generator terminal in a circuit including resistor I31 75 and the resistor H8 in the circuit otfiuxmeter connected in series relation with the coil of resistor I29. The capacitor I is thus arranged to charge or dischargewhen the voltage of generator I changes through the resistor II! and thereby insert a component of voltage in the circuit of coil 90 of the monitor fluxmeter to suppress hunting. A switch Ill may be provided, if desired, to discharge :capacitor I" if the current standard is to be removed from its compartment.

The heater circuit 52 is provided to maintain the temperature of the current standard compartment 48 at a constant value and, as illustrated, this heater circuit comprises a heater element I38 preferably positioned near the bottom oi' the compartment with .thermostat III and suitable fuse elements I 40, all. connected in series relation to be energized from the alter natlng current supply circuit II.

. The operation of the current standard in the regulatin system illustrated is substantially as iollowsi If the switch I20 is open the device as shown is a voltage regulator on generator I. When I20 is closed, the value of this voltage held is modified in such a way as to maintain constant current. The current standard compares a component of voltage from the current shunt Ill and a component of voltage derived from the standard voltage obtained from resistor 88 and its associated voltage divider resistors. The difference voltage thus obtained is amplified to modify the generator voltage obtained from the voltage divider I24 when switch I2. is closed. When switch I 20 is closed, the grid ofthe amplifier tube 40 assumes the average voltage of tap I" on resistor I26 and the anode voltage of tube 0. This average voltage varies in accordance with the operation of the monitor fluxmeter 50. When the voltage component across the shunt H9 is greater than the standard reference voltage, the fiuxmeter coil 90 rotates to throw more light on phototube I05. More light on phototube I increases the positive potential of grid II: of tube H0 and causes this tube to conduct more current. The increase of current in the circuit of tube III! tends to lower the average potential of grid 43 of the amplifier tube. As a result, the tube 40 conducts less current and the direct current of saturating coil 28 is decreased so as to reduce the output of the rectifier 8 and therebydecrease the excitation of generator I to establish an equilibrium condition between the voltage component of shunt H9 and the standard of reference as established across resistor 88.

While Ihave shown and described my invention as'applled to a particular system of connections and as embodying various devices diagrammatically shown, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A standard of reference of an electric quantity comprising a source of constant voltage, a compensated galvanometer including means for producing a magnetic field and -a coil winding having a torsional suspension rotatably mounted within said magnetic field, an impedance connected in series relation with said source of concoil 80 to the positive side of generator I through 'of constant voltage.

8 said impedance to produce a voltage thereacross, and means continuously and substantially eoincidently responsive to the position of said coil for controlling said last mentioned means to maintain the voltage drop across said impedance equal and opposite to the voltage of said source 2Q A standard of reference of an electric quantity comprising a standard cell, is compensated galvanometer including means for producing a magnetic field and a coil winding having a torsional suspension rotatably mounted within said magnetic field, a resistor connected in series relation with said standard cell and said coil, an electronic tube connected to circulate a current through said resistor for producing a voltage drop thereacross equal and opposite to the voltage of said standard cell, and means continuously and substantially coincidently responsive to the position of said coil for controlling the conductivity of said-electronic tube.

3. A standard of reference of an electric quantity comprising a standard cell, a compensated galvanometer comprising means for producing a magnetic field and a coil winding having a torsional suspension rotatably mounted within said magnetic field, a resistor connected in series relation with said standard cell and said coil, an

electronic tube connected to said resistor for said resistor equal and opposite to the voltage of said standard cell.

4. A standard of reference of an electric quantity comprising a standard cell, a compensated galvanometer comprising means for producing a magnetic field and a coil winding having a torsional suspension rotatably mounted within said magnetic field, a resistor connected in a series circuit with said standard cell and said coil, switching means connected in said series circuit, an electronic tube having an anode-cathode circuit connected to circulate a current continuously through said resistor for producing a voltage drop thereacross equal and opposite to the voltage of a standard cell, light sensitive means controlled in response to the position of said coil for coincidently controlling the conductivity of said electronic tube, and means responsive to the cur rent in the anode-cathode circuit of said electronic tube for controlling said switching means.

5. A standard of reference of an electric quantity comprising a standard cell, a first compensated galvanometer including means for producing a magnetic field and a coil winding having a torsional suspension rotatably mounted within said magnetic field, a first resistor connected in series relation with said standard cell and said coil, means responsive to the position of said coil for maintaining the voltage drop across said resistor equal and opposite to the voltage of said standard cell, means including a second resistor for deriving a component of voltage from said first resistor, a second compensated galvanometer including means for producing a magnetic field stant voltage and said coil, means for'energizing fl and a coil winding having a torsional suspension sis-mete I 'otatably mounted within said magnetic field, neans having a variable "component of voltage hereacross connected in series relation with said aecond resistor andthe coil of said second galanometer, means for controllingsaid variable :omponent of voltage, and means responsive to he position of the coil of said second galvanom- :ter for controlling said last mentioned means.

6. A standard of reference of an electric quanity comprising a standard cell, a first compenaated galvanometer including means for proiucing a magnetic field and a coil winding having i torsional suspension rotatably mounted within iaid magnetic field, a first resistor connected in :erles relation with said standard cell and said :oil, a first electronic tube connected to circulate 10 voltage subject to variation connected in a series circuit with said source of constant voltage and said coil, means including an electronic tube havprovided with one winding connected in the :urrent through said resistor for producing a zoltage drop thereacross equal and opposite to the voltage of said standard cell, light sensitive neans controlled in response to the positionv of and a coil winding having a torsional suspension rotatably mounted within said magnetic field, neans having a. variable component of voltage thereacross connected in series relation with said second resistor and the coil of said second galvanometer, means for controlling said variable :omponent of voltage, a second electronic tube for controlling said last mentioned means, and a second light sensitive means responsive to the position or the coil of said second galvanometer for controlling said second electronic tube.

7. A standard of reference of an electric quantity comprising a standard cell, a first compensated galvanometer including means for producing a magnetic field and a coil winding having a torsional suspension rotatably mounted within said magnetic field, a first resistor connected in series relation with said standard cell and said coil, a first electronic tube connected to circulate current through said resistor for producing a voltage drop thereacross equal and opposite to the voltage 01' said standard cell, light sensitive means controlled in response to the position of said coil for controlling the conductivity of said electronic tube, means including a second resistor for deriving a component of voltage from said first resistor, a second compensated galvanometer including means for producing a magnetic field and a coil winding having a torsional suspension rotatably mounted within said magnetic field, means having a variable component of voltage thereacross connected in series relation with said second resistor and-the coil of said second galvanometer, means for controlling said variable component of voltage, ,-a second electronic tube for controlling said last mentioned means, inductive means provided with one winding connected in series relation with said second electronic tube and a second winding in mutual inductive relation with said first winding connected in series relation with the coil oi said second galvanometer, and a second light sensitive means responsive to the positionoi' the coil of said second galvanometer for controlling saidsecond electronic tube.

8. A standard of reference of an electric quantity comprising a source oi constant voltage, a

compensated galvanometer comprising means for I producing a magnetic field and a coil winding having a torsional suspension rotatably mounted within said magnetic field. a second source of anode-cathode circuit of said electronic tube and a second winding'in mutual inductive relation with said first winding connected in series relation with said coil, and means responsive to the position of said coil for varying the conductivity of said electronic tube to maintain equilibrium between said second source of voltage and said source of constant voltage, r

9. A standard of reference of an electric uuan tity comprising a source of constant voltage, a compensated galvanometer comprising means for producing a magnetic field and a coil winding having a torsional suspension rotatably mounted within said magnetic field, a second source of voltage subject to variation connected in a series circuit with said source or constant voltage and said coil, means including an electronic tube having an anode-cathode circuit for controlling said second source of variable voltage, inductive means provided with one winding connected in the anodecathode circuit of said electronic tube and a second winding in mutual inductive relation with said first winding connected in series relas tion with said coil, means responsive to the posi tion of said coil for varying the conductivity of said electronic tube to maintain equilibrium between said second source of voltage and said source of constant voltage, and means for delay ing a change in the conductivity of said electronic tube upon a change in the position of said coil.

10. A standard of reference of an electric quan-- tity comprising a standard cell, a first compen sated galvanometer including means for producing a magnetic field and a coil winding having a torsional suspension rotatably mounted within said magnetic field, a first resistor connected in series relation with said standard cell and said coil, means responsive to the position of said coil for maintaining the voltage drop across said resistor equal and opposite to the voltage of said standard cell, means including a second resistor for deriving a component of voltage from said first resistor, a second compensated galvanometer including means for producing a magnetic field and a coil winding having a torsional suspension rotatably mounted within said magnetic field, selective switching means for energizing. at will the coil of either galvanometer to cause operation of either coil to a desired position in its associated magnetic field, means having a variable com-- ponent of voltage thereacross connected in series relation with said second resistor and the coil of said second galvanometer, means for controlling said variable component of voltage, and means responsive to the position of the coil of said second galvanometer for controlling said last mentioned means. t

-11. A standard of reference of an electric quantity comprising a standard cell, a first compensated galvanometer including means for producin a magnetic field and a coil winding having a torsional suspension rotatably mounted within said magnetic field, a first resistor connected in series relation with said standard cell and said coil, means responsive to the position of said coil for maintaining the voltage drop across said resistor equal and opposite'to the voltage of said standard cell, a voltage divider comprising a see- 7 0nd resistor having an adjustable contact arm 4 0nd galvanometer, a second voltage divider including a resistor having an adjustable contact arm and connected to be responsive to the voltage of said electric circuit, means for simultaneously operating said contact arms, means for controlling the voltage 01 said electric circuit. and means 16 12 responsive to the position of the coil of said second galvanometer for controlling said last mentioned THEODORE A. HIGH.

REFERENCES CITED The following reterenicee are 0! record in the file or this patent:

UNITED STATES PATENTS Number Name Date 1,939,443 Geiselman Dec. 12, 1933 2,404,891 Bchmitt July 30, 1946 3,424,146 Caldwell et a1. July 15. 1947 

